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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f03660e3a9f8f6ed3e4b5eb7c3b3afb9010344be4b1bb0f10a0d56d40a1b34cb' 
  AND token = 'CgFlomRmMZiEPBTAFlOCK3EAwkRkoxxzhqRBR2pRmXY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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