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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d6b8f0b4cb8b3d11db2527a22a64c245befed9577615b76983acd475bb352cf' 
  AND token = '+6VH4ryP2iYqOC7UaPQXX+vM668KZ5UyaUn+sSrya38=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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