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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5ef576659d3d0ea0b25ad6b8213d25446b982de08e4714e8fc4d8c39c8bc629f' 
  AND token = '+HkSC4ggNZ1ZYvRWrTd6PUSLZHPIEEA2vWwdkQ2RBL8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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