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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f4847f50d6d89632f4a015a67be2d453c9cc8dca9623dd5be14dc71ccd793f90' 
  AND token = 'fsFZ0ENrlFjt6GtQ+Y+Gx/e2VEtkkd5jX97+Jv5ygxQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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