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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f3ef10b7f509a7a2f20faa1ea7bd48005da378fa6f068a5ad30a0d37af16705' 
  AND token = 'g8KDUCX9rEPeTrFStxLJUup5wqry25nH+11k5SgEAH4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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