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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c66b20d0932e4461d7c5dee339ef3c3954d3361370e63a0515d6ea1a607b1ad4' 
  AND token = 'P31Ud/Ap1QBdmMKt8WUkNvtMZoz9wxoYn+2EkQluTMc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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