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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc5b9b9c8ae36da770f763a7ef9c75cd545511d63ed2ebcaa5626579a11f3b28' 
  AND token = 'f+4I3cGrDaChRPNaEjVLmZGKVWdwmlXKyAUbAu2XQlw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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