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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c9d2d6c9f0a316bd300f80eb3689aee3ecde1789bb345cbd8a442eed75501a38' 
  AND token = 'Cnr4rc0I+LMzCzCTQBPM9Tu8cSfZNz9jNsCrUsjrc/A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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