SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51426c27b8342a6e762c151215f5ad4629f3bfd72e23eb2b05cf2ce0678fa916' 
  AND token = 'KbJFWpmzOnEqFWazGkjqQmMc1OIrFe3jhSng/zXPBW4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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