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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'abd6f894a03c28d7efae9b43a5faf2603b3ec0b2e1c1e9a40920a9d846268db9' 
  AND token = 'u/C/E/2tfLTuGsD3LOEqUwIIvKDMV0HVgm5pkv/4DUY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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