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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a21387ec3073a7a0b3c529edec3b00d0cd5f19c822e47894d5c10350fa1a5bdd' 
  AND token = 'tlncnSupdF4zXfkZ+ir1jE4iSjFpZDfQkRUnDvxR3fo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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