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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3d354df99d92f4aa97c3d8638332f76aa2d78914ab8d49523511c9e276a381f' 
  AND token = '+cZXbjdCegciqHXvM4CUajmksMpEBJG14RV2NxxaizM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}