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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f6d39c6c647fb34378a4fa47656d0743ca41cbdd2a1f0b32b0290d18231ce60c' 
  AND token = 'zf+u/fK0yDSdjKx2gZ5Lcsft8cxwtVZwaePU1UWp/NE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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