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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3c715919cbf2f079a37456ca87f7d2f106563ddb2f6b0905989eaa060e34c14' 
  AND token = 'kqaD79ukTnwjmtdtdhUO+1bhP3kgjc5qN4o/gr52Y4Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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