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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5ff4ef49f05bc39a076e2a8038afe5608846477f5ac4ce62bcfe7ae5308367a' 
  AND token = 'fl4mZs8Oi1qT3Tp6U1Ck9i+P72XPizdcqy2gurP1OyI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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