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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df77932434dde53c517993589bc9da2256af9c1cc86bf11357021df483247e94' 
  AND token = 'iLfFAqbPN9YlEm4iouudXNO+KMqbwcNt2JTEUOku7Lg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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