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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd3c349383636314dc0e97b1e6a3d62deb1cf53a1c3a5e28e6c8f1421768aa29d' 
  AND token = '71d9+IpH5jreBsUa/9oEOuR7q31CIPsbLtwFrzmcLco=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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