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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4574cb68d00a696f6e256e7da85a81df37de5450c179dde87046b5925e3acdf2' 
  AND token = '8WDzW8V9izdrJFgJDTRGm+ksG5cvcPKimR+3REcBELo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}