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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a51e6c7f67028e44a4f3ecce5a8eb868bb09357423b55dc15f3073b4fbdd9e6e' 
  AND token = '/aoj/BJbE6xkZTCWQC8KKs/ibhUDAUWSc3bSqMncu7Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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