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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9fadb1cbd5b8390d7a00f627a057fb40c10c23cfe1a0d926c37ca22be3c438d' 
  AND token = 'PN+pFRKMh/p5fdZPjPI4EpwsVxP6ix/Yy9MbPienXn8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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